Studies are being carried out to further define the nature of functional and structural changes during development. These studies are being carried out in newborn dogs, rats and pigs. The studies utilize both in vivo and in vitro techniques. Some of the determinations include organic anion and cation transport, total renal blood flow, intrarenal blood flow distribution, acid base balance, electrolyte excretion, plasma renin and aldosterone concentration. Effects of nutrition, asphyxia, and other stresses will be studied. Effects of various drugs will also be investigated. BIBLIOGRAPHIC REFERENCE: Lu, L-T, M.D. Bailie, J. B. Hook. Effect of antidiuretic hormone and theophylline on cyclic amp in renal medulla of newborn and adult rabbits and dogs. Comp. Biochem. Physiol. 6:181-185, 1975.